Newer Whooping Cough Vaccines Fall Flat

Action Points

Youngsters who received older whole-cell whooping cough vaccines had greater protection during a recent outbreak than those who got newer acellular medications.

Point out that the findings, from a large case-control study, add to the growing evidence of shortcomings of the newer acellular vaccines.

Youngsters who received older whole-cell whooping cough vaccines had greater protection during a recent outbreak than those who got newer acellular medications, researchers reported.

During a 2010-2011 outbreak in California, 10- through 17-year-olds whose first four diphtheria/tetanus/pertussis shots included acellular whooping cough vaccine were nearly six times as likely to get the disease as those who had four whole-cell vaccinations, according to Nicola Klein, MD, PhD, and colleagues at the Kaiser Permanente Vaccine Study Center in Oakland.

And they were nearly four times as likely to get the disease as were youngsters who got a mixture of the two types of vaccines, dubbed DTaP and DTwP, respectively, Klein and colleagues reported online in Pediatrics.

The findings, from a large case-control study, add to the growing evidence of shortcomings of the newer acellular vaccines.

All three analyses focused on different aspects of the California outbreak, the largest in the state in more than 50 years.

The most recent findings raise the question of trade-offs in vaccines, commented Robert Frenck, MD, of Cincinnati Children's Hospital Medical Center.

The whole-cell vaccine was replaced in the first place because it had side effects, such as fever, that were unpleasant for children and "scary" for parents, he told MedPage Today.

The acellular version has fewer side effects, he said, but the trade-off may be immunity that is more short-lived.

The original studies that led to licensing of the acellular vaccine, he said, suggested it was efficacious for as long as the whole-cell version. "Subsequent studies are showing that may not be true," he said.

Whether the public would want to return to the whole-cell vaccine is an open question, he added, but the findings raise the question of whether it might be worthwhile to try to "tweak" the acellular medication to improve its longevity.

For the most recent study, Klein and colleagues looked at children and young teens who were vaccinated during the period when the U.S. was changing from the whole-cell vaccine to the newer acellular version. Those participants, born in 1994 through 1999, were 10 through 17 during the outbreak.

The researchers analyzed data from youngsters who had four pertussis-containing vaccines during the first 2 years of life at Kaiser Permanente Northern California.

During the outbreak, 138 youngsters tested positive for whooping cough by polymerase chain reaction (PCR) and formed the cases. The researchers considered two control groups -- the 899 who were tested by PCR but were negative, and 54,339 who were not tested but were matched to the cases by sex, race or ethnic group, and medical clinic.

Among the 1,037 participants who were tested by PCR, 234 only got whole-cell doses in the first 2 years of life, 197 got a mix, and 606 only got acellular vaccines, the researchers reported.

When Klein and colleagues compared the cases with PCR-negative controls:

Those who had four DTaP shots had an odds ratio for a positive pertussis test of 5.63, with a 95% confidence interval from 2.55-12.46, compared with those who had four DTwP shots.

Those who had a mix of types had an odds ratio for a positive pertussis test of 3.77, with a 95% confidence interval from 1.57-9.07, compared with those who had four DTwP shots.

Among the 234 tested participants who got four DTwP shots, only eight (or 3.4%) had whooping cough, they found, while among the 606 who only got acellular vaccines, there were 111 positive tests, or 18.3%.

The 197 who got a mix of vaccine types had an intermediate risk -- 19 cases, or 9.6%.

Results were similar when they compared the cases with the larger control group, Klein and colleagues reported.

The study was supported by Kaiser Permanente. Klein and co-author Roger Baxter, MD, report research support from GlaxoSmithKline, Sanofi-Pasteur, Pfizer, Merck & Co, Novartis, and MedImmune. The pertussis vaccines purchased by Kaiser Permanente Northern California, which are the focus of this study, were manufactured by (among others) GlaxoSmithKline, Wyeth (now Pfizer), Sanofi-Pasteur, and Merck.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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